An Australian Orion aircraft has identified several orange objects in the southern Indian Ocean in what is being described as "the most promising leads" in the search for missing Malaysia Airlines flight MH370.

Crew on board the aircraft spotted the objects, each greater than two metres in size, in a five-nautical-mile area within the search zone.

The Australian Maritime Safety Authority (AMSA) says yesterday's weather in the area was "reasonable" with reported visibility greater than 10 kilometres, and Flight Lieutenant Russell Adams says he is hopeful of finding more objects if favourable conditions continue.

"For my crew and from our perspective, this was the most visibility we [have] had in the water of any objects ... and gave us the most promising leads," he said.

Flight Lieutenant Adams says the objects will now be assessed to determine whether they are related to the missing airliner.

"I must stress that we can't confirm the origin of these objects ... the details of these, in association with a GPS buoy have been passed on to our rescue coordination centre," he said.

The latest finding comes as Prime Minister Tony Abbott reiterates his commitment to the continuing search for MH370 which he says is building momentum. There are now 1,000 sailors scouring the ocean for debris.

"I'm certainly not putting a time limit on it," he said.

"As I said, we owe it to the families, we owe it to everyone who travels by air, we owe it to the governments of the countries who had citizens on that aircraft," he said.

An Australian Navy vessel has been equipped with two different devices to help locate the flight data recorders from flight MH370, as a US navy captain says finding surface debris remains a "critical" first step.

The US has provided specialist equipment and operators for the Ocean Shield vessel, which was expected to leave for the search area today.

US navy captain Mark Matthews says the first device is a towed pinger locator, which listens for acoustic emissions from the flight data recorders, and the second is an underwater vehicle.

"Once we get a detection from this pinger [locator] we would put the underwater vehicle in the water to conduct a side scan, to map the debris field," he said.

"That same system can be equipped with a camera to then collect photographic evidence of what is in the bottom [of the ocean]."

Locating point of impact 'critical'

Captain Matthews, a director of ocean engineering with the US navy, says it is critical the crash site is identified before the recorders can be located.

"My team's role is to conduct an underwater search, if we can find surface debris, and then track it back to a probable point of impact," he said.

"It is critical that we find that surface debris so we can reduce the area that we'd need to conduct an underwater search in."

Captain Matthews was involved in the search for an Air France jet which crashed into the Atlantic Ocean in 2009 and says in that instance, they had a good idea where the plane went down, but it still took a long time to locate the wreckage.

"The pingers were non-functional on that aircraft due to the damage it received when it hit the water," he said.

The ABC's Jade MacMillan describes what it is like on board a P3 Orionsearching the southern Ocean for a missing airliner.

"It then took over two years conducting side scan sonar searchers with vehicles to locate the debris.

"Right now the search area is basically the size of the Indian Ocean, which would take an untenable amount of time to search," Captain Matthews said.

"If you compare this to Air France flight 447, we had much better positional information of where that aircraft went into the water."

Eight ships and nine aircraft spent Sunday scouring a massive area in the Indian Ocean west of Perth, trying again to find some trace of the aircraft, which went missing more than three weeks ago and is presumed to have crashed in one of the most remote areas on the planet.

"This represents the greatest number of ships tasked in the search to date," AMSA said in a statement on Sunday night, adding that 252,000 square kilometres were searched.

That move followed new analysis of radar and satellite data that concluded the Boeing 777 travelled faster and for a shorter distance after vanishing from civilian radar screens.

Ex-Defence Force chief takes lead role in search

Former Australian Defence Force chief Angus Houston will take a leading role in coordinating the international search effort, Prime Minister Tony Abbott said on Sunday.

The retired Air Chief Marshal will head a new Joint Agency Coordination Centre to be set up in Perth.

"I will be coordinating with my people at the international level, at the national level and of course most importantly, with the families and the media," he said.

His role will be to maintain clear lines of communication between all of the international partners as well as with the families of the passengers, many of whom are expected to travel to Australia as the search progresses.

Australia has also issued countries involved in the search with a set of protocols to abide by should any wreckage be found.